[PATCH v14 07/18] list_lru, shrinkers: introduce list_lru_shrink_{count,walk}

Vladimir Davydov
2013-12-16T12:17:20Z

NUMA aware slab shrinkers use the list_lru structure to distribute
objects coming from different NUMA nodes to different lists. Whenever
such a shrinker needs to count or scan objects from a particular node,
it issues commands like this:

count = list_lru_count_node(lru, sc->nid);
freed = list_lru_walk_node(lru, sc->nid, isolate_func,
isolate_arg, &sc->nr_to_scan);

where sc is an instance of the shrink_control structure passed to it
from vmscan.

To simplify this, let's add the special list_lru functions to be used by
shrinkers, list_lru_shrink_count() and list_lru_shrink_walk(), which
consolidate the nid and nr_to_scan arguments in the shrink_control
structure.

This will also allow us to avoid patching shrinkers that use list_lru
when we make shrink_slab() per-memcg - all we will have to do is extend
the shrink_control structure to include the memcg to scan from and make
list_lru_shrink_{count,walk} handle this appropriately.

Thanks to David Chinner for the tip.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
---
fs/dcache.c | 14 ++++++--------
fs/gfs2/quota.c | 6 +++---
fs/inode.c | 7 +++----
fs/internal.h | 7 +++----
fs/super.c | 22 ++++++++++------------
fs/xfs/xfs_buf.c | 7 +++----
fs/xfs/xfs_qm.c | 7 +++----
include/linux/list_lru.h | 16 ++++++++++++++++
8 files changed, 47 insertions(+), 39 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 6055d61..7e66fca 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -972,24 +972,22 @@ dentry_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg)
/**
* prune_dcache_sb - shrink the dcache
* @sb: superblock
- * @nr_to_scan : number of entries to try to free
- * @nid: which node to scan for freeable entities
+ * @sc: shrink control, passed to list_lru_shrink_walk()
*
- * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
- * done when we need more memory an called from the superblock shrinker
+ * Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
+ * is done when we need more memory and called from the superblock shrinker
* function.
*
* This function may fail to free any resources if all the dentries are in
* use.
*/
-long prune_dcache_sb(struct super_block *sb, unsigned long nr_to_scan,
- int nid)
+long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
{
LIST_HEAD(dispose);
long freed;

- freed = list_lru_walk_node(&sb->s_dentry_lru, nid, dentry_lru_isolate,
- &dispose, &nr_to_scan);
+ freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
+ dentry_lru_isolate, &dispose);
shrink_dentry_list(&dispose);
return freed;
}
diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
index 98236d0..09a32c4 100644
--- a/fs/gfs2/quota.c
+++ b/fs/gfs2/quota.c
@@ -132,8 +132,8 @@ static unsigned long gfs2_qd_shrink_scan(struct shrinker *shrink,
if (!(sc->gfp_mask & __GFP_FS))
return SHRINK_STOP;

- freed = list_lru_walk_node(&gfs2_qd_lru, sc->nid, gfs2_qd_isolate,
- &dispose, &sc->nr_to_scan);
+ freed = list_lru_shrink_walk(&gfs2_qd_lru, sc,
+ gfs2_qd_isolate, &dispose);

gfs2_qd_dispose(&dispose);

@@ -143,7 +143,7 @@ static unsigned long gfs2_qd_shrink_scan(struct shrinker *shrink,
static unsigned long gfs2_qd_shrink_count(struct shrinker *shrink,
struct shrink_control *sc)
{
- return vfs_pressure_ratio(list_lru_count_node(&gfs2_qd_lru, sc->nid));
+ return vfs_pressure_ratio(list_lru_shrink_count(&gfs2_qd_lru, sc));
}

struct shrinker gfs2_qd_shrinker = {
diff --git a/fs/inode.c b/fs/inode.c
index 4bcdad3..37962eb 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -748,14 +748,13 @@ inode_lru_isolate(struct list_head *item, spinlock_t *lru_lock, void *arg)
* to trim from the LRU. Inodes to be freed are moved to a temporary list and
* then are freed outside inode_lock by dispose_list().
*/
-long prune_icache_sb(struct super_block *sb, unsigned long nr_to_scan,
- int nid)
+long prune_icache_sb(struct super_block *sb, struct shrink_control *sc)
{
LIST_HEAD(freeable);
long freed;

- freed = list_lru_walk_node(&sb->s_inode_lru, nid, inode_lru_isolate,
- &freeable, &nr_to_scan);
+ freed = list_lru_shrink_walk(&sb->s_inode_lru, sc,
+ inode_lru_isolate, &freeable);
dispose_list(&freeable);
return freed;
}
diff --git a/fs/internal.h b/fs/internal.h
index 4657424..3db5f6e 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -14,6 +14,7 @@ struct file_system_type;
struct linux_binprm;
struct path;
struct mount;
+struct shrink_control;

/*
* block_dev.c
@@ -107,8 +108,7 @@ extern int open_check_o_direct(struct file *f);
* inode.c
*/
extern spinlock_t inode_sb_list_lock;
-extern long prune_icache_sb(struct super_block *sb, unsigned long nr_to_scan,
- int nid);
+extern long prune_icache_sb(struct super_block *sb, struct shrink_control *sc);
extern void inode_add_lru(struct inode *inode);

/*
@@ -125,8 +125,7 @@ extern int invalidate_inodes(struct super_block *, bool);
*/
extern struct dentry *__d_alloc(struct super_block *, const struct qstr *);
extern int d_set_mounted(struct dentry *dentry);
-extern long prune_dcache_sb(struct super_block *sb, unsigned long nr_to_scan,
- int nid);
+extern long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc);

/*
* read_write.c
diff --git a/fs/super.c b/fs/super.c
index e5f6c2c..13c4c92 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -78,27 +78,27 @@ static unsigned long super_cache_scan(struct shrinker *shrink,
if (sb->s_op->nr_cached_objects)
fs_objects = sb->s_op->nr_cached_objects(sb, sc->nid);

- inodes = list_lru_count_node(&sb->s_inode_lru, sc->nid);
- dentries = list_lru_count_node(&sb->s_dentry_lru, sc->nid);
+ inodes = list_lru_shrink_count(&sb->s_inode_lru, sc);
+ dentries = list_lru_shrink_count(&sb->s_dentry_lru, sc);
total_objects = dentries + inodes + fs_objects + 1;

/* proportion the scan between the caches */
dentries = mult_frac(sc->nr_to_scan, dentries, total_objects);
inodes = mult_frac(sc->nr_to_scan, inodes, total_objects);
+ fs_objects = mult_frac(sc->nr_to_scan, fs_objects, total_objects);

/*
* prune the dcache first as the icache is pinned by it, then
* prune the icache, followed by the filesystem specific caches
*/
- freed = prune_dcache_sb(sb, dentries, sc->nid);
- freed += prune_icache_sb(sb, inodes, sc->nid);
+ sc->nr_to_scan = dentries;
+ freed = prune_dcache_sb(sb, sc);
+ sc->nr_to_scan = inodes;
+ freed += prune_icache_sb(sb, sc);

- if (fs_objects) {
- fs_objects = mult_frac(sc->nr_to_scan, fs_objects,
- total_objects);
+ if (fs_objects)
freed += sb->s_op->free_cached_objects(sb, fs_objects,
sc->nid);
- }

drop_super(sb);
return freed;
@@ -119,10 +119,8 @@ static unsigned long super_cache_count(struct shrinker *shrink,
total_objects = sb->s_op->nr_cached_objects(sb,
sc->nid);

- total_objects += list_lru_count_node(&sb->s_dentry_lru,
- sc->nid);
- total_objects += list_lru_count_node(&sb->s_inode_lru,
- sc->nid);
+ total_objects += list_lru_shrink_count(&sb->s_dentry_lru, sc);
+ total_objects += list_lru_shrink_count(&sb->s_inode_lru, sc);

total_objects = vfs_pressure_ratio(total_objects);
drop_super(sb);
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index c7f0b77..a2bb6a33 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1563,10 +1563,9 @@ xfs_buftarg_shrink_scan(
struct xfs_buftarg, bt_shrinker);
LIST_HEAD(dispose);
unsigned long freed;
- unsigned long nr_to_scan = sc->nr_to_scan;

- freed = list_lru_walk_node(&btp->bt_lru, sc->nid, xfs_buftarg_isolate,
- &dispose, &nr_to_scan);
+ freed = list_lru_shrink_walk(&btp->bt_lru, sc,
+ xfs_buftarg_isolate, &dispose);

while (!list_empty(&dispose)) {
struct xfs_buf *bp;
@@ -1585,7 +1584,7 @@ xfs_buftarg_shrink_count(
{
struct xfs_buftarg *btp = container_of(shrink,
struct xfs_buftarg, bt_shrinker);
- return list_lru_count_node(&btp->bt_lru, sc->nid);
+ return list_lru_shrink_count(&btp->bt_lru, sc);
}

void
diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
index 14a4996..65bc404 100644
--- a/fs/xfs/xfs_qm.c
+++ b/fs/xfs/xfs_qm.c
@@ -761,7 +761,6 @@ xfs_qm_shrink_scan(
struct xfs_qm_isolate isol;
unsigned long freed;
int error;
- unsigned long nr_to_scan = sc->nr_to_scan;

if ((sc->gfp_mask & (__GFP_FS|__GFP_WAIT)) != (__GFP_FS|__GFP_WAIT))
return 0;
@@ -769,8 +768,8 @@ xfs_qm_shrink_scan(
INIT_LIST_HEAD(&isol.buffers);
INIT_LIST_HEAD(&isol.dispose);

- freed = list_lru_walk_node(&qi->qi_lru, sc->nid, xfs_qm_dquot_isolate, &isol,
- &nr_to_scan);
+ freed = list_lru_shrink_walk(&qi->qi_lru, sc,
+ xfs_qm_dquot_isolate, &isol);

error = xfs_buf_delwri_submit(&isol.buffers);
if (error)
@@ -795,7 +794,7 @@ xfs_qm_shrink_count(
struct xfs_quotainfo *qi = container_of(shrink,
struct xfs_quotainfo, qi_shrinker);

- return list_lru_count_node(&qi->qi_lru, sc->nid);
+ return list_lru_shrink_count(&qi->qi_lru, sc);
}

/*
diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index 3ce5417..194b1c4 100644
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -9,6 +9,7 @@

#include <linux/list.h>
#include <linux/nodemask.h>
+#include <linux/shrinker.h>

/* list_lru_walk_cb has to always return one of those */
enum lru_status {
@@ -75,6 +76,13 @@ bool list_lru_del(struct list_lru *lru, struct list_head *item);
* Callers that want such a guarantee need to provide an outer lock.
*/
unsigned long list_lru_count_node(struct list_lru *lru, int nid);
+
+static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
+ struct shrink_control *sc)
+{
+ return list_lru_count_node(lru, sc->nid);
+}
+
static inline unsigned long list_lru_count(struct list_lru *lru)
{
long count = 0;
@@ -114,6 +122,14 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
unsigned long *nr_to_walk);

static inline unsigned long
+list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
+ list_lru_walk_cb isolate, void *cb_arg)
+{
+ return list_lru_walk_node(lru, sc->nid, isolate, cb_arg,
+ &sc->nr_to_scan);
+}
+
+static inline unsigned long
list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
void *cb_arg, unsigned long nr_to_walk)
{
--
1.7.10.4